The present invention concerns a method in the reeling of a paper web or equivalent, in which the web is reeled by supporting the rolls to be formed on its circular, cylindrical outer circumference by means of at least two supporting members of which the first one, in the direction of arrival of the web, is a driven carrier roll with the web being passed to reeling over a sector thereof. Furthermore, this carrier roll forms a reeling nip supporting the roll being wound from below. A press member, preferably a press roll, is used above the roll being wound, by means of which the roll being wound is maintained stably in reeling position.
The present invention further concerns a reel-up mechanism for a paper web or equivalent, including at least two supporting units of which the first one in the direction of arrival of the web, is a carrier roll provided with a mechanical rotating drive, with the web being passed to reeling over a sector thereof. This carrier roll forms a reeling nip supporting the roll from below. This reeling-up mechanism also includes a press member unit, preferably a press roll unit, by means of which the reeled-up web roll is stably maintained in reeling position.
With respect to prior art related to the present invention, references is made to the following patents and applications: U.S. Pat. Nos. 3,098,619; 3,346,209; 4,456,190; 4,485,979; 4,485,980; GB Pat. Appl. No. 2,142,909; German Offen. DE-OS No. 3,121,039; Finnish Pat. No. No. 49,276; and Finnish Patent Applications Nos. 843184 and 844652.
In the forming of paper rolls reeled up while being supported on the circumference thereof, there has been a problem of internal damage in the large and heavy rolls reeled up. Damage is produced, in particular, underneath the surface layer of the reeled-up roll. Some of the most common damage results in crepe wrinkles in a transverse direction of the web, and in web cracking The principal cause of damage has been ascertained to be an excessively high nip pressure between the paper roll being wound and the carrier roll, resulting from the weight of the paper roll or from an excessive press-roll load.
In order for a roll of good quality to be obtained by means of a carrier-roll reel-up, it has been noted that the linear load between the paper roll being wound and the carrier roll should be about 1 to 4 kN/m. Within this range of linear load, it is possible, as a rule, to accomplish desired distribution of tension in the roll.
When a carrier roll of short radius is used, the above range of linear load is exceeded at the final stage of the reeling with large paper rolls so wound, whereby the contact pressure rises to a level greater than that tolerated by a printing-paper roll. This results from the narrow nip area between the paper roll and the carrier roll. In a manner known in the prior art, attempts have been made to eliminate this problem by making the carrier roll larger, which increases the cost of manufacture and operation of the reel-up.
A soft-faced carrier roll is known from Finnish patent application No. 843,184, in which the nip face becomes larger. However, a drawback in this arrangement is the dynamic problem of formation of two faces, as well as the generation of heat during the reeling.
Attempts have also been made to solve these problems by dividing the load on carrier rolls of different sizes or on inclined carrier rolls. Distribution of the load between rolls does not reduce the maximum pressure, but it increases the pressure between one of the carrier rolls and the paper roll, depending on the diameters and on the inclinations. The most uniformed distribution of the roll pressure is obtained with equally large carrier rolls situated symmetrically underneath the paper roll, by using the construction known from U.S. Pat. No. 4,456,190.